This invention relates generally to semiconductor integrated circuit packages and more particularly, it relates to an improved high density leaded ball-grid array (BGA) package of a simple construction which includes a leadframe mounted on a top side of a laminated substrate and solder balls attached to the bottom side thereof so as to accommodate a higher lead-count.
In recent years, there has existed a high level of interest in the area of ball grid array (BGA) package and assembly technology. The reason for this is because the package and interconnection industry has departed from the use of pins as connectors for electronic packaging due to their high cost of fabrication, the high failure rate of connections, and the limitations on the density of input/output pins. As a result, solder balls have been used which are superior to pins in the above areas as well as being surface mountable.
As is generally known heretofore, ball-grid array (BGA) semiconductor packages typically include a substrate such as a printed circuit board and a semiconductor chip or die mounted on the top side of the substrate. A conductive trace pattern is also formed on the top side of the printed circuit board. The die generally contains a number of electrical circuits therein and includes a plurality of bonding pads disposed on its top surface adjacent its peripheral edges. Very thin gold bonding-wires have their one ends bonded to the corresponding pads on the integrated-circuit die and their other ends bonded to the corresponding ends of the conductive trace pattern on the top side of the printed circuit board. A second conductor trace pattern is formed on the bottom side of the printed circuit board and is electrically connected to the first conductive trace pattern on the top side thereof through respective plated-through holes. Each of the ends in the second conductive trace pattern terminates with a contact pad where a conductive solder ball is attached thereto. Generally, the semiconductor die and the bonding-wires are encapsulated in an encapsulating material such as a plastic molding compound.
The consumers of the BGA packages in the electronic and computer industries have been demanding higher and higher die densities to support higher lead counts within the same package footprint area. Further, the consumers are likewise demanding improved conductor routing to the package so as to produce enhanced electrical performance and to reduce costs. While some package designers have attempted to solve these problems by utilizing multi-layer substrates, this use of increased number of substrates is generally more expensive and has thus increased manufacturing costs.
Accordingly, there exists a need for an improved high density leaded BGA package which can accommodate the electronic and computer industry's demand for a smaller pitch distance between the conductor solder balls in order to provide higher lead counts within the same conventional package size. It would also be expedient to provide an improved high density leaded BGA package which is of a simple construction and is relatively low in cost to manufacture and assemble, but yet still has a high electrical performance.